1. Field of the Invention
This invention relates to a transmission technical field, and more particularly to a time synchronization method and a time synchronization device for a mobile communication system.
2. Description of the Prior Art
With the development of mobile communication techniques, Code Division Multiple Access 2000 (CDMA2000), Wideband Code Division Multiple Access (WCDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) mobile communication systems require high precision time synchronization.
The problem of time synchronization in a base station can be solved by employing a Global Positioning System (GPS) module in each base station. However, in view of national security and low cost, there are some other ways to fulfill time synchronization. For example, satellite time sources are collected, information on satellite time is sent to respective base stations through a terrestrial transmission network, without employing a GPS module in each base station. Since it is not necessary to install a GPS module in a base station, cost can be reduced and national security can be guaranteed. When transmitting time information via a network, the time information is delivered among devices through respective time transmission protocols and time ports.
However, in a conventional time synchronization device, different time transmission protocols and different time ports are irrelevant to each other. The following problems may appear as a result:
1. When a time synchronization device has two or more time transmission protocols and/or time ports, preferably one of the transmission protocols and ports is manually selected through the time synchronization device. However, since these protocols are independently operated, even if the time information of a time transmission protocol which is selected as a port are degraded or invalid, the time transmission protocol will still be preferably used because it is a preconfigured time transmission protocol. Therefore, the flexibility and reliability of the device are decreased.
2. if a part of network A uses one type of time transmission protocol and port, and a part of network B uses another type of time transmission protocol and port, when A transmits time information to B, the status of time information may be lost and an error may happen during selecting time information in B because of the difference between two types of time transmission protocols and ports.